Good Structures for Balsa Wood Towers

Balsa wood is only the third lightest wood in the world, but it is strong. Engineering students build balsa wood towers (or bass wood towers) to learn how to build strong structures. It is an excellent exercise, and students learn a lot doing it. Many designs are readily available, but designing and building your own towers is how you learn. There are two basic types of balsa wood tower structures: three-legged towers and four-legged towers.

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Four-Legged Towers

Balsa wood towers with four legs are easier to build, but they are not usually as structurally sound as their three-legged counterparts. The bracing strip of a tower with four legs only needs to be angled in one direction. Bracing strips are the supporting beams of the legs of the tower. Solid wood legs should not be completely square. The braces need to be equal distances apart all the way up the legs. The wood can also be laminated in strips for good strength. The Eiffel Tower is a good example of a four-legged structure.

Three-Legged Towers

Three-legged towers are harder to build because the angles are more difficult, but they tend to be stronger towers. The braces of three-legged towers must run in two different directions, as opposed to the braces of four-legged towers that only need to run in one direction. The wood can be laminated into strips with a three-legged tower just like a four-legged tower. The braces need to be spaced evenly no matter which type of structure you choose to build.

Wood Grain

The wood grain dictates the flexibility and rigidness of the wood as much as the density of the wood. There are three types of wood grains: A-grain, B-grain and C-grain. A-grain wood has long fibres and is very flexible. It becomes even more flexible when soaked in water. A-grain is excellent for use in pieces that need to be formed, but it is a poor choice for pieces that need to be stronger. B-grain wood fibres are shorter than A-grain, but they are also stronger. B-grain is also called random cut. It is suitable for general purposes, but in many uses A-grain or C-grain are more suitable. C-grain is stiffer, and the fibres of the wood grain are shorter. C-grain is the strongest of the three. It is necessary to become familiar with the three types to determine which grain is most suitable for certain purposes.

The Design

First draw the design on paper before you begin building a tower. Begin with a more general design and work in the detail as you develop the design. Draw the design to scale using graph paper. Use the design to build the tower. Once the tower is built, test the strength. Find the weak points in the design and construction of the tower and make adjustments to build stronger towers. Trial and error is the name of the game in building balsa wood tower structures.